Title : Salt tolerance in plants; lessons learnt from mangroves
Abstract:
Salinity is one of the most deleterious abiotic stress factors that affects crop yield and reduces crop productivity. Increasing soil salinity poses a threat to food security globally. Excessive accumulation of toxic ions such as Na+ and Cl- in plant cells leads to osmotic imbalance as well as ion toxicity. Mangroves such as Avicennia officinalis have evolved adaptations such as ultrafiltration at the roots aided by apoplastic cell-wall barriers to thrive in saline conditions. We characterized Cytochrome P450 genes, AoCYPs from A. officinalis and their Arabidopsis orthologs AtCYPs. We show that they are involved in apoplastic barrier formation and are induced within 30 minutes of salt treatment in the roots. Heterologous expression of AoCYPs in Arabidopsis T-DNA insertional mutants and wild-type rice conferred increased NaCl tolerance to seedlings by enhancing root suberin deposition leading to reduced Na+ accumulation in the shoots. Histochemical staining and GC-MS/MS quantification of suberin precursors confirmed the role of CYPs in suberin biosynthesis. Using chromatin immunoprecipitation, yeast one-hybrid and luciferase assays, we identified AtWRKYs as the upstream regulator of AtCYPs in Arabidopsis. In addition, the atwrky mutants exhibited reduced suberin and salt sensitive phenotypes, which were rescued by expressing 35S::AtCYPs in atwrky mutants. This further confirms that the regulation of AtCYPs by AtWRKYs is part of the salt tolerance mechanism, and our findings can help in generating salt tolerant crop plants.
